Breaking/exit nested for in vb.net

How do I get out of nested for or loop in vb.net?

I tried using exit for but it jumped or breaked only one for loop only.

How can I make it for the following:

for each item in itemList
for each item1 in itemList1
if item1.text = "bla bla bla" then
exit for
end if
end for
end for
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小开

Put the loops in a subroutine and call return

小开
最佳答案

Unfortunately, there's no exit two levels of for statement, but there are a few workarounds to do what you want:

  • Goto. In general, using goto is considered to be bad practice (and rightfully so), but using goto solely for a forward jump out of structured control statements is usually considered to be OK, especially if the alternative is to have more complicated code.

    For Each item In itemList
For Each item1 In itemList1
If item1.Text = "bla bla bla" Then
Goto end_of_for
End If
Next
Next


end_of_for:

  • Dummy outer block

    Do
For Each item In itemList
For Each item1 In itemList1
If item1.Text = "bla bla bla" Then
Exit Do
End If
Next
Next
Loop While False

    or

    Try
For Each item In itemlist
For Each item1 In itemlist1
If item1 = "bla bla bla" Then
Exit Try
End If
Next
Next
Finally
End Try

  • Separate function: Put the loops inside a separate function, which can be exited with return. This might require you to pass a lot of parameters, though, depending on how many local variables you use inside the loop. An alternative would be to put the block into a multi-line lambda, since this will create a closure over the local variables.

  • Boolean variable: This might make your code a bit less readable, depending on how many layers of nested loops you have:

    Dim done = False


For Each item In itemList
For Each item1 In itemList1
If item1.Text = "bla bla bla" Then
done = True
Exit For
End If
Next
If done Then Exit For
Next
小开

Make the outer loop a while loop, and "Exit While" in the if statement.

小开

I've experimented with typing "exit for" a few times and noticed it worked and VB didn't yell at me. It's an option I guess but it just looked bad.

I think the best option is similar to that shared by Tobias. Just put your code in a function and have it return when you want to break out of your loops. Looks cleaner too.

For Each item In itemlist
For Each item1 In itemlist1
If item1 = item Then
Return item1
End If
Next
Next
小开 
For i As Integer = 0 To 100
bool = False
For j As Integer = 0 To 100
If check condition Then
'if condition match
bool = True
Exit For 'Continue For
End If
Next
If bool = True Then Continue For
Next
小开

If I want to exit a for-to loop, I just set the index beyond the limit:

    For i = 1 To max
some code
if this(i) = 25 Then i = max + 1
some more code...
Next`

Poppa.

小开

Insert a boolean value check in your loop:
If MyBreak Then
Exit Sub
End If
Where MyBreak is toggled by a button or label clicked.


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